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Surfactant protein D (SP-D) is one of four known protein components of the pulmonary surfactant lining the lung alveoli. It is involved in immune and allergic responses. SP-D occurs as a tetramer of trimers. Trimerization is thought to be initiated by a coiled coil domain. We have determined the solution structure of a 64-residue peptide encompassing the coiled coil domain of human SP-D. As predicted, the domain forms a triple-helical parallel coiled coil. As with all symmetric oligomers, the structure calculation was complicated by the symmetry degeneracy in the NMR spectra. We used the symmetry-ADR (ambiguous distance restraint) structure calculation method to solve the structure. The results demonstrate that the leucine zipper region of SP-D is an autonomously folded domain. The structure is very similar to the independently determined X-ray crystal structure, differing mainly at a single residue, Tyr248. This residue is completely symmetric in the solution structure, and markedly asymmetric in the crystalline phase. This difference may be functionally important, as it affects the orientation of the antigenic surface presented by SP-D.

Solution structure of the coiled-coil trimerization domain from lung surfactant protein D., Kovacs H, O'Ddonoghue SI, Hoppe HJ, Comfort D, Reid KB, Campbell D, Nilges M, J Biomol NMR. 2002 Oct;24(2):89-102. PMID:12495025

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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Categories: Homo sapiens | Campbell, I D. | Comfort, D. | Donoghue, S I.O. | Hoppe, H J. | Kovacs, H. | Nilges, M. | Reid, K B.M. | Ambiguous distance restraint | Coiled coil | Lung surfactant protein | Nmr-spectroscopy | Trimer